This invention relates generally to micromechanical diffractive phase gratings that are also known as grating light valves for display applications.
A micromechanical phase grating includes a plurality of ribbon-shaped reflectors that may be selectively deflected to diffract incident light. In one embodiment, the phase grating includes parallel rows of ribbon reflectors. If alternate rows of reflectors are flexed downwardly relative to the other reflectors, incident light may be diffracted.
When the reflectors are all in the same plane, incident light is reflected back on itself. By blocking that light that returns along the same path as the incident light, a dark spot may be produced in a viewing system.
Conversely, when alternate reflectors are deflected, the diffracted light may be at an angle to the incident light which may bypass the blocking element that blocks light returning along the incident light path. This diffracted light then produces a bright spot in the viewing system.
Thus, a phase grating may be created which selectively produces light or black spots. In addition, gray scales and color variations may be produced in some embodiments.
One problem with conventional designs for micromechanical reflection phase gratings is that they are formed on the silicon substrate. That substrate may include other high value components fabricated beneath the phase grating. Thus, if the phase grating is not formed properly, the entire silicon-based device may be ruined. This greatly increases yield problems and therefore fabrication costs.
Therefore, it would be desirable to have a way to form micromechanical reflection phase gratings in a way which does not risk the finished silicon wafer when defects occur in the formation of the micromechanical phase grating.